The last time Rep. Dana Rohrabacher offered an amendment on the House floor to protect states rights when it came to legalization of medical marijuana, it was defeated 163–262.

Since that vote in 2012, four states — Illinois, Massachusetts, New Hampshire and Maryland — passed laws or regulations allowing for the use of medical marijuana, bringing the total to 21 states and the District of Columbia.

Now, supporters of medical marijuana anticipate the strongest vote yet on a states-rights amendment when the fiscal 2015 Commerce-Justice-Science appropriations measure (HR 4660) comes to the House floor in a few weeks, while lawmakers are weighing offering additional marijuana provisions on appropriations measures.

Most, but not all, of the proposals lawmakers are considering bringing up are aimed at protecting state laws and programs on medical marijuana use.

The chief provision, which will be offered as an amendment to the appropriations bill funding the Commerce and Justice departments, would prohibit the federal government from prosecuting medical marijuana users and providers who are abiding by their state’s law.

The House has voted on similar proposals six times since 2003, with about 150 to 160 members supporting it each time.

But advocates expect that more lawmakers than ever will support the bipartisan proposal this year, which will likely be introduced by two California lawmakers, Rohrabacher, who is a Republican, and Democrat Sam Farr. Boosters expect to win new backers this year because of the increasingly high poll numbers supporting legalization.

“Congress is really good at jumping in front of the parade, and now the parade has been built,” said Bill Piper, director of national affairs at the Drug Policy Alliance.

In a January CNN poll, 88 percent of respondents said adults should be allowed to legally use marijuana for medical purposes if it is prescribed by a doctor. In October 2013, a Gallup poll showed for the first time that a majority of respondents, 58 percent, supported legalizing recreational use of marijuana.

Dan Riffle, director of federal policies at the Marijuana Policy Project, said lawmakers are beginning to get the message that “this is something that most people support, and it’s not going to help you get elected if you stand in the way of marijuana reform.”

That increasing support may lead lawmakers to hold additional marijuana policy votes on other appropriations bills.

Rep. Ed Perlmutter, D-Colo., may consider offering an amendment to the Financial Services appropriations measure that would help marijuana businesses get access to banking by updating federal rules, according to his office. An aide for Colorado Democrat Jared Polis said he also may offer marijuana policy amendments, although he has not made a decision yet.

Not all of the provisions being considered would be aimed at expanding marijuana access. This month, House Appropriations Chairman Harold Rogers, R-Ky., told C-SPAN “Newsmakers” that he feels the Obama administration has failed to enforce federal law by allowing Colorado and Washington to legalize adult recreational use of marijuana.

When asked if he would put language addressing that lack of enforcement in forthcoming appropriations bills, Rogers said, “Well, it remains to be seen.”

Rogers added, “It’s federally a criminal matter. So I have great concern that the administration is again selectively enforcing the law.”

Expanding legal use of marijuana, whether for medical or recreational purposes, is not a party-line issue. Enough Democrats and Republicans oppose expanded legalization that the Rohrabacher amendment, or any like it, is expected to fail.

Most recently, the House defeated 195–222 a proposal from Oregon Democrat Earl Blumenauer that would have allowed veterans to talk with Veterans Affairs medical providers about participating in state marijuana programs. The proposal was offered as an amendment to the bill (HR 4486) funding the Department of Veterans Affairs and military construction programs.

Opposites Attract

The backers of the Rohrabacher amendment are an unusual group of social liberals and conservatives who see legalization as a states’ rights issue. Lawmakers including Blumenauer, Michigan Republican Justin Amash and Texas Republican Steve Stockman have voted for it in the past.

Georgia Republican Paul Broun, a physician who supports the amendment, said in a statement that the provision makes sense “from both a medical perspective and a Constitutional perspective.” He added, “This amendment would ensure that medical marijuana patients adhering to their state’s laws would not be punished by an overreaching federal government.”

Riffle said that if supporters could reach every member who rests ideologically between the amendment’s expected co-sponsors, “we’d have 435 votes.”

Farr offered the states-rights amendment at the House Appropriations markup this month, but then withdrew it. He noted that 15 members of the panel come from states that have legalized medical marijuana use.

“It’ll be a matter of time — it’ll be soon — that Congress will make some adjustments” to federal marijuana policy, he said.

But Riffle and Piper do not expect the growing number of state laws legalizing medical marijuana to affect how lawmakers vote on the proposals. Of the 50 Democrats who opposed the Rohrabacher amendment in 2012, six come from states that have since allowed for legal medical marijuana use.

“I don’t know how many people are going to switch their vote based on the fact that their state has recently passed a medical marijuana law,” Riffle said.

But state efforts are prompting some lawmakers to move forward with other measures. Rep. Morgan Griffith, R-Va., recently introduced a bill (HR 4498) to prohibit the federal government from preventing the use of marijuana for medical purposes in compliance with state law, and reclassify marijuana to a Schedule II drug, which would put fewer restrictions on it.

Back in 1979, Virginia passed measures to allow the use of medical marijuana to treat glaucoma and cancer, but federal law blocks those measures, according to Griffith’s office.

Griffith said he will not offer his bill as an amendment to any appropriations bills, however, because “I don’t think it’s the right way to deal with this legal issue.”